The present invention relates generally to the field of gemstones, e.g. diamonds, and more specifically to the field polishing and faceting gemstones. In particular, the present invention is directed toward a new design for a tang and a dop.
Gemstone polishing is an old art going back many centuries. In many ways the practice of gemstone polishing remains the same today as it did long ago. Gemstone polishing required a steady and firm structure to hold the gemstone, a stable platform to hold the gemstone in the desired position, and polishing surface for polishing the gemstone.
These requirements led to the development of the dop (typically a piece of lead into which the gemstone was imbedded with the surface to be polished exposed) to hold the gemstone, the tang to hold the dop and provide a stable platform, and the polishing wheel (usually mounted on a table called a sleigh) against which the desired surface of the gemstone may be held to be polished. These developments provided gemstone polishers with tools that allowed them greater control over the polishing process.
As noted above, in gemstone polishing the tang is a device for holding the dop. The tang basically comprises two main parts: the butt which is the wooden rear end and the clamp which is made of steel and extends forward from the butt. The butt is broad at the rear with a fiat top on which the fiat lead weights can be placed when pressure on the tang is required. Beneath the butt are two legs which rest on the steel plate of the bench. At the rear is the tail or steel rod which helps to hold the tang in position when placed in the sleigh.
The clamp's neck is fixed to the fore-end of the butt. The front or head of the clamp is split and held together by a bolt and nut. When the nut is tightened the clamp shuts and holds the copper stalk of the dop in a groove near the end of the head.
The dop is the apparatus that holds the gemstone in proper position for polishing. Dops were originally made from lead but have many different shapes and some even resemble the chuck of drill.
Essentially, the combination of the tang and the dop with a gemstone creates a three pointed structure with the gemstone as the third point. The third point that is the gemstone rests on the polishing wheel as it operates. In this manner each facet of the gemstone is polished.
The present invention is directed at improvements in the dop, mounting the dop to the tang, and the tang itself. Current tangs have a fairly complex structure, including springs, that make adjustment difficult. The present invention provides a tang of unique and simple design that requires no springs or tails and is easily adjusted and readjusted. Also, the tang of the present invention is designed to present a stable base regardless of the height of the tang.
Further, the manner in which the dop is currently constructed and connected to the tang results in a limited arc of movement. This limited arc of movement is 0 to 50 degrees. The pivot point is the end of the dop and not the gemstone. Accordingly, the polisher must take the size of the gemstone, a diamond for example, into account when positioning the dop and the tang for polishing. The present invention by a unique and simple design eliminates this problem by allowing the polisher to use the gemstone itself as the reference or pivot point and at the same time allows the user a potential arc of movement of -5 to 90 degrees. This allows the polisher to easily polish or facet gemstones at angles that have hither to been unobtainable.
The inventor knows of no prior art that either teaches or shows the technology of the present invention. The most authoritative prior art reference of which the inventor is aware regarding this technology in the book Diamond Cutting, By Basil Watermeyer, 4th ed., printed and bound by Perskor, Doornfontein, Johannesburg, South Africa.